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Hans and Zacharias Janssen invent the first compound microscope by placing two lenses in a tube -
Robert Hooke made a simple microscope and observed a piece of cork -
Anton van Leeuwenhoek designed his own microscope and found living organisms in pond water, milk, and various other substances; discovered what are now called protozoans -
Scientists discover the cell nucleus -
Mathias Schleiden studied plant tissues and concluded that plants are made of cells. -
Scientists propose that both plants and animals are made of cells -
Rudolph Virchow proposed cells are made from the division of existing cells. -
Ernst Ruska developed the electron microscope -
Ernst Everett Just writes the textbook Biology of the Cell Surface -
The scanning tunneling microscope allows scientists to see individual atoms